I had a look on the wiki and found these bits, but nothing about spiders posioning you..
- Zombies drop a new item instead of feathers, Rotten Flesh.
- New Enderman mob: die in water, drop diamonds.
- Totally new, fractal-based biome code includes 7 new biomes.
- Food no longer heals directly but indirectly. If above a certain point, heals about half a heart every 5 seconds.
Obviously subject to change. Hopefully the diamond drops do. Seems stupid.
The diamonds drop is only for pax not going to be in official release. Btw my source was IGN and official MC forums